Thermally operated electrical circuit breaker



Patented Aug. 10, 1954 THERMALLY OPERATED ELECTRICAL CIRCUIT BREAKER Joseph E. Straub, Manhattan Beach, and Lex W. Hubbard, .l'rx, Los Angeles, Calif.

Application October 13, 1951, Serial No. 251,154 11 Claims. (Cl. 200116) Our invention relates generally to electrical circuit protectors, and more particularly to thermally operated overload circuit breakers.

In providing a circuit breaker oi the kind to which the invention relates, there a number of special features which should he incorporated, depending somewhat upon the use or application to which the device is put. For example. the present circuit breaker is designed with the requirements of aircraft in mind, but it will be appreciated that the device is not restricted to this field, but be used wherever its features advantageous,

Among such features may be mentioned the arran ement of the parts in a housing of small oensions which conform to military specifications, and be interchangeably mounted with other similar standard components in military as well as civilian planes. In addition, the housing of our overload circuit breaker is substantially dust-proof, thus avoiding deterioration of the contacts from the deposit of dirt thereon, and mintnizing fire hazards due to arcing during the opening of the breaker contacts.

Although the dimensions of the device should be small, the parts shoul be rugged so that long life full eiiiciency in operation are ensured, and addition the parts should be few in numher to facilitate any repair or replacement of parts that may be necessary.

With the above-mentioned requirements in mind and with others later referred to, it is an object of our invention to provide a thermallyoperated circuit breaker comprising relatively few parts of ample strength arranged in a small dustproof ce which can be very simply installed in place as removed for repair or inspecaction, thus ensuring that remain clean provide for the current.

wide separation thereof, while a double gap form of construction h advantage of affordin additional ticn between the contacts, particularly de- .e high altitude or wherever heavy currents are con rolled.

another object of the invention to mount the movable contacts of the circuit breaker or" our invert on individual resilient members so that proper en agement is assured between the fixed and movable contacts, the arrangement being such that there is no substantial current flow through the resilient mounting members, thus preventing the danger of deterioration of such members due to heat generated by the flow of electric current therethrough.

A further object of our invention is to provide 2 a thermallymperated circuit breaker which also may be manually operated, and in at least one form, the manually operable means may be used to hold the device in closed circuit condition during emergency conditions, despite the overload that would normally trip the breaker.

A still further object of the invention is to provide a thermally-operated circuit breaker having various advantageous features, yet comprising relatively few parts adapted to be quickly ace assembled into a complete unit.

Further features and objects of our invention will hereinafter appear from the f -lowing speciiication describing preferred embodiments of our invention illustrated in the accompanying drawings, in which:

Fig. l is a vertical cross-section of a preferred form of the overload circuit breaker constructec according to our invention, the section the device is mounted, the parts being shown in the circuit closed position;

Fig. 2 is a fragmentary perspective view of the carrier mechanism for the movable contacts shown in Fig. 1;

. 3 is a cross-section on the line of Fig. l;

4 is a perspective View, drawn on a larger scale of the contact support shown in Figs. 1 and 2;

Fig. 5 is a View similar to Fig. 1, but showing the circuit breaker in open position, a portion of the inward end of the manual operating member being sectioned to show the shape thereof;

ig. 6 is a perspective View of the current carry g members of our circuit breaker, with the fixed and movable contacts separated open circuit position;

Fig. 7 a vertical cross-section taken just within side wall of the housing of a modded form of the invention, showing the circuit circuit closed position, the position of a e strip just before manual opening of the circuit breaker being shown in dotted lines;

Fig. 8 a central vertical section through the device shown in Fig. 7, but showing the parts in open circuit position;

Fig. 9 is a fragmentary cross-section on the line 2-9 of Fig. 7;

1c is a perspective View of the movable contact carrier down in Figs. 7 and 8 Fig. 11 is a perspective view of a bimetallic part utilized in all the illustrated embodiments of our invention;

Fig. 12 is a cross-section on the line I2-l2 of Fig. 7;

Fig. 13 is a vertical sectional view through a second modified form of the device; and

Fig. 14 is a view similar to Fig. 13, but showing the device in an open-circuit position.

Referring now to Fig. 1 of the drawings, the

numeral 28 indicates a case or housing, preferably of insulating material in which all the mechof the device is enclosed. The illustrated case is in the form of a narrow box having an open side or top with flanges 2i at the upper ends thereof. The open side of the case is closed by a plate 22 secured to flanges 2! by suitable tamper-proof means such as a hollow rivet 23, and the plate is formed with a central opening surrounded by an upstanding flange 25.

A lug 28 is secured toward one end of the bottom of: the case 28, the lug projecting outwardly of the casing through a slot 27! to provide one terminal of the circuit breaker to which a wire 01' lead of an electrical circuit may be connected. second lug 30, having a generally Z-shape, is secured to the opposite end of the bottom of the case, and a fixed contact 32 is mounted on the upper horizontal arm of the lug til.

A third lug 33, best seen in Figs. 3 and 6, has a vertical portion secured to the adjacent end wall of the case and its upper end extends horizontally to receive second fixed contact 3% in lateral alignment with fixed contact 32. The lower end of lug 33 projects through a slot in the bottom of the case 23 to provide the other terminal of the circuit breaker. To reduce the opportunity for dust to enter the case or housing 26, the slots 2? and 35 may be closed with a sealing compound (not shown) in any wellknown manner.

A movable contact member, generally indicated at 38, and best shown in Fig. 4, is adapted to bear against fixed contacts 32 and 3'5 and complete a circuit from one to the other. Member 38 preferably consists of a plate 38 having resilient arms it and M, at the ends of which are mounted movable contacts d2 and 43, respective ly, adapted to engage against fixed contacts 32 and 35. A flexible conductor M extends between movable contacts M and 13 to provide a bridging connection, while permi ting limited independent movement of the movable contacts.

Plate as is mounted on a movable contact support, generally indicated at 55, which comprises a plate-like base 55 to which plate 35 is attached. A lug 17 extends upwardly from the base 46 and has a hole 58 in its upper end, while an arm .9 projects laterally from the upper end of the lug in a manner similar to a bell-crank.

The movable contact support at is attached. to a movable contact arm 59, preferably formed. of insulating material, which is pivoted at one end on a pin 55 passed through the arms of a small bracket 52 secured to the top plate 22. A spring 53 has one end secured to the bracket 52 and the other end attached to the arm 59 to snap the free end of the contact arm upwardly when freed from a bimetallic latching member described hereinafter which holds the arm is downward position when the circuit breaker is closed.

The contact support lug G? is pivotally attached to arm to near the free end of the arm by a pin 54, and a tension spring 55 is connected between the projection of plate 39 and a projection 56 at the pivoted end of the contact arm. The action of the spring 55 is to urge the contact support t5 carrying the movable contacts Q2 and 3, about the pin 5% in a manner to separate the movable contacts from the fixed contacts 32and 35. As seen in Figs. 1 and 5, this rotation of the contact support is in a clockwise direction.

A bimetallic member, generally indicated at 60 and best shown in Figs. 6 and 11, is of generally inverted U shape, having one arm ti that is turned backward near its end and secured to lug while arm E2 is bent forwardly and connected to lug 3E. This connection of the bimetallic strip is identical in all the illustrated embodiments and provides an electrical path, when the device is in circuit-closed position, from one leadin lug, through one arm of the bimetallic member, through abridge portion 5S connecting the arms, through the other arm and through the double movable and fixed contacts L2, 53, and 3'2, respectively, and the other lead-in lug. As an additional safety precaution, independently of the normal operation of the circuit breaker, the bimetallic member 59 may be so proportioned as to fuse at a predetermined point under a current overload greater than the norcurrentdnterrupting setting of the device.

At its free end, the bimetallic member 5E3 is provided with an inturned catch or tang G3 which engages the upper end surface of contact arm where a metal plate or sear 6 31 is preferably located to reduce the wear on the softer arm. The free end of the bimetallic member is also provided with fingers 65, 58 which are bent forwardly and then backwardly and upwardly for cooperation with a manually operable member by which the circuit breaker may be manually tripped. The horizontally extending arm 49 of the movable contact support is of a length to bear against the upper end of the bimetallic member between fingers t5 and 65, above the tang as, when the member is in its normal condition adapted to hold the contact arm 56 in lowered position. Under these conditions, the arm :29 engages the bimetallic member 58 before the tang $3 engages the sear t l, and continued downward movement of the arm to latched position will rotate contact support 35 and bring the movable contacts into position to engage with the fixed contacts.

In order to adjust and calibrate the action of the circuit breaker after it has been assembled, we form the bimetallic member G5 with a re -entrant portion toward its. fixed end, affording an angular knee 8'5. A heat-resistant slidable wedge 68- is located on the surface of lug 25 and may be adjustably forced against the knee ill to stress it to a greater or less degree, thereby controlling the amount of heating of the bimetallic member 6% required to release the contact bar 5 13.

The wedge 53 is adjusted by a small threaded rod 69 working in a threaded hole provided in the wedge and provided with a. collar ll) bearing against the adjacent end wall of the case. The outer end of the rod 69 projects into a hole formed in said wall and is slotted that the position of the wedge may be adjusted from the exterior of the case by the use of a small screw driver. After adjustment, the hole in the case may be filled with sealing wax or the like. thus preventing tampering with the setting of the device. The further the wedge is forced under the knee 5'! of the bimetallic member, the greater is the force required to free the catch 63 from the contact arm 59 and therefore the greater is the current that will be carried by the bimetallic member before tripping the circuit breaker.

The manual operating member of the device comprises a plunger H having ahead 12 (Fig. 2) whose undersurface is channeled to receive the contact arm to without interfering with the operation of arm 39, the inner face of the head preferably being formed to afford line contact with the upper surface of the contact arm as shown in Fig. 5. If desired, a wear piece '53 of suitable material may be inserted in the head at the area of contact with arm 5 The side faces of the head 52 formed to internt slidably with the inner faces of the side walls of the case and are thereby guided for vertical movement. As shown in the drawings by way or example, the side faces of the head 52 are formed with vertical grooves i l (Fig. 2) that receive ribs on the walls of the case. in order to provicle a visual signal the device is tripped, we prefer to have that portion of the plunger ll that is always visible colored black, for example, while that portion which is hidden from sight when the circuit is closed, colored red, for example. In this manner, when the circuit breaker is trip ed and the plunger it is extended up wardly, a red portion will be visible.

llie edge or" head if: is provided with cars races '56 and "i? that engage with fingers and of the bimetallic member, the cam faces ll slog-n ing backward, toward the pin from their lower to their upper ends. In this manner, up-

vard movement of the head causes the cam faces and ii to force the and away from the contact arm or 11 the latter is released from the catc t3. An enlarged cap may conveniently be applied to the outer end of the plunger to enable the plunger to be more easily grasped and moved. The manually operable parts are preferably made of insulatingmaterial, as are the contact arm and case 2% so that there is no danger of current flow to exterior parts of the device. i urther, there is no substantial current flow through any primarily resilient or spri g members and consequently deterioration of sucl due to heating by the electric current is prevented.

hi the operation of our device, the circuit is closed by pressing inwai on the cap 53 on plunger Ti, thereby pivoting the contacts 5t ainst the urging of the sprii 5 5, in a clockcdirection as seen in gs. 1 and 5. The arm of contact support, originally held in its released position by spring as seen in 5, en ages the upper end of the bimetallic member as the contact 5t pivots, and the contact support rotates about the pin t l in counterclockwise direction as the plunger it continues its inward travel. lortly before the tang 63 snaps over the sear the movable contacts 32 and d3 engage the contacts and and are thercai wiped across fixed contacts by reason of t as he pivoting of the contact sup ort thereby ensurin ootl rica-l connec ion.

To open the circuit the cap with attached plunger ii is pu d outwardly, thus shov ing the head i2 upwar ly so that the cam faces '16 '5? force the fingers and 55 of the bimetallic meinbcr so from the contact i353. This the tang 63 from the sear 6d, and the contact arm 5b snaps upwardly, in

a countercloclnvise direction, as seen in Figs. 1 and 5, separating the movable contacts Q2 and 15 from fixed contacts 32 and 35.

When the circuit breaker is closed and an overload. occurs, the bimetallic member is heated by the passage or current through it, the heat being suifioient to distort the member ternporarily, causing it to move away from the coin tact arm 5:! and disengage the tang 53 from the sear E l. The movable contacts 42 and thus separate from the fixed contacts 32 and 25, as described in the manual opening of the breaker.

Should an attempt be made to keep the circuit breaker closed by pressing inwardly on the cap 78 on plunger H while an overload occurs, the breaker will still open. This trip free operation is very desirable where it is essential that an overload not be permitted to exist for any length of time. In our breaker, such operation is provided by the action of the contact support 55 which is pivotally mounted on the contact arm 5c. It will be appreciated that when the bimetallic member 523 is moved away from the contact arm 59 to release the latter, the end of the arm d9 of the contact support die is also re leased from engagement with the upper end of the bimetallic member. The spring 55 immediately snaps the contact support d5 about the pin 54, in a clockwise direction e n in Figs. 1 and 5, separating the movable cc and 43 from the fixed contacts and and opening the circuit. This action of tie movable contacts will occur whether the contact arm is necessary to open the circuit.

The embodiment of our invention shown in Figs. 7 through 12 differs i: that shown in Figs. 1 through 6 in. that the movable cont. cts are mounted directly on the contact arm.

It is not thought necessary to again o parts identical with, or lly di r from, those already described and such pars ar indicated by the same numerals as F gs. through 6, with the addition of the letter a, in Figs. 13 and 14, by addition of the le ter 2).

contact arm preferably l insulating material, is pivoted a pin secured in the of a mounted on the case plate connected to the contact a fi A is 1 a manner to snap the arm upwardly, away from the fixed oontacts 32a and 35a, when the arm is released from engagement with member In this connection, the latching and release or" the contact arm at by the bimetallic member 385 is similar to the corresponding opera formed by the contact arm and ins 1noludlug the bimetallic me her shown in Fig. t c circuit through the device can be bro '1 by pulling out the plunger ii since by so doing the cam face on the head 12 or T211 will engage the fingers 65, 66 on the free end of the inernb and push the catch 63 off the end of the conta arms.

In the form of the invention she" 11 in Figs. '1 through 12, in distinction to the form shown in Figs. 1 through 6, the circuit breaker contacts can be held closed, although the bimetallic membcr may have released the contact by l .nua-lly pressing down the operating plunger cap 15a. Such a procedure would obviously only be used when an emergency arises that requires the closing of an electrical circuit regardless of the possible damage to equipment that may be connected thereto. As an example, emergency operation of certain equipment on an airplane is sometimes necessary to prevent a crash.

In the embodiment of the invention illustrated in Figs. 13 and 14, a pivotable handle M32 is employed instead of the plunger operating means of the other embodiments illustrated. The circuit breaker is mounted in a case 36 that may be open on one side and covered by a plate (not shown) secured to the case by any suitable means. The case 86 is formed with an outwardly angled side 88 on which are supported the fixed contacts 89, which are double but in which only the one nearest the observer is seen in the Figures 13 and 14.

The bimetallic member 6% is attached to the bottom of the case and a lead-in lug 9! is connected to one leg Gib of the bimetallic member, and extends outwardly through a slot 82 in the wall of the case. A screw or terminal as is provided on the end of the lug at for securing an electrical lead to said lug. The other arm 62b of the bimetallic member 682) is secured to the bottom of the case, and a lug 95 is also connected to the latter arm, one fixed contact as being mounted on this lug.

A third lug so is secured to the angularly positioned wall 88, and the second fixed contact is mounted on lug so, which is extended through the wall of the case and fitted similarly to lug iii.

The movable contact assembly, generally indicated at 3%, is mounted directly on a contact arm er pivoted at one end on a pin 98 secured in the case. A spring 9% is connected to the contact arm 9'! to snap the arm upwardly about its pivot when released by the bimetallic member this.

The manual operating member comprises a molded member W1! with a body portion it! having an arcuate periphery fitting in an arcuate re cess in the top of the case 86. A finger piece 32 projects through a slot in the wall of the case and communicates with the recess. The operating member lilli is'pivoted on a pin use mounted in the side wall 594 of the case 85, the operating member being arranged to substantially close the slot through the wall of the case in all positions. The surface of the body portion liii, opposite the finger piece E52, is formed to provide a cam H engaging against the surface of the contact arm 97, the lobe of the cam bearing against the contact arm at all times. In circuit-open position, the finger piece Hi2 will be held to one end or" the slot in the case as shown in Fig. 14, and is moved to the opposite end of the slot to close the breaker contacts.

In order to manually trip the device, the body portion ii is provided with further cam portions formed on the edges of a pair or" plates Hi6 lying against the sides of the contact arm 3? with their edges contacting the fingers extending from the free end of the bimetallic member. The contour of cam plates 5% is such that in the circuit-open position shown in Fig. 14, the fingers are pushed away from the contact arm so that catch 63b is pushed off the contact arm. In the circuit-closed position, the cam plates its permit the fingers to move toward the contact arm and the catch 63b to engage over the end thereof if the bimetallic member is in normal condition and has not been flexed away from the contact arm by the efiects of heat due to an overload current.

It will be seen that in the embodiment of the invention described with reference to Figs. 13 and 14, the contacts of the circuit breaker may be held closed manually in emergency.

It will be noted that the circuit breaker of our invention, although of simple construction, may be produced in forms adapted to various conditions, and preferably is mounted in a completely closed case. In the form shown in Figs. 1 through 1 the fixed contacts and bimetallic member and initial adjustment or preloading means for the latter, are mounted in the case, while the movable contacts, contact arm, spring or springs, and manually operable means are mounted on a cover plate. This arrangement makes for rapid production since one production line can assemble the parts carried by the case and another line can assemble the parts mounted on the plate secured to the case.

In the form shown in Figs. 13 and 14, all parts are mounted on the case, but can be easily positioned through the open side of the case. Adjusting or preloading means for the bimetallic member, such as the slidable wedge 63 shown in the preferred form, may be readily incorporated in this embodiment if desired.

Each form of the invention may be used as an on-off switch, though they are not designed primarily for this purpose. A wiping contact between fixed and moving contacts is provided by mounting the movable contacts on a pivoted contact arm so that the movable contacts are dragged over the fixed contact surfaces in reaching finally engaged position.

It will be appreciated that while we have described the various forms of our circuit breakers as having a top, bottom, side, etc., these words, as well as the descriptions upper, lower, etc. are used for convenience in describing the devices as shown in the draw ngs. Since the circuit breakers are not dependent upon the force of gravity for their operation, but instead rely upon resilient means such as springs, the breakers will operate satisfactorily in any position, in addition to that shown in the drawings.

While we have particularly described and shown embodiments of our invention at present considered preferable by us, it is to be understood that various changes and modifications may be made in said embodiments by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

We claim:

1. A circuit breaker including: a mounting member supporting the circuit breaker parts; a bimetallic member having a pair of arms connected together at one end, and secured at their other ends to the mounting member in series in an electric circuit; means projecting from the connected together ends of said arms; fixed contact means secured to said mounting member; a movable contact arm; movable contact means mounted on said contact arm; a catch mounted on said bimetallic member and adapted to engage with said contact arm when the latter is in circuit-closed position to hold the movable contact means against the fixed contact means and to release said arm when the bimetallic member is distorted by heat generated by an electric current exceeding a predetermined value; means tending to snap said contact arm and movable contact means carried thereby away from the fixed; contact means when the contact arm is released by said catch on the bimetallic member; and manually operable means having a part engaging against the contact arm and a cam face formed on said part adapted to engage with the means projecting from the bimetallic member to force the catch on the latter member on" th contact arm when said manually operable member is moved in one direction, and to engage said contact arm with said catch when moved in the opposite direction and the bimetallic member is in undistorted condition.

2. A circuit breaker including: a bimetallic member having a pair of arms connected together at one end, one arm being connected at its other end to a lead of an electric circuit in the circuit breaker is incorporated; a first nxed contact connected to the other arm of the bimetallic member; a movable contact arm guided for movement toward said fixed contact; a pair of movable contacts mounted on the contact arm and connected together by a conductive one of said movable contacts being arranged to and break circuit with the first fixed contact; a second fixed contact insulated from the first contact and connected to a lead of the elect 'ic circuit, the second movable contact being arranged to make and break contact with said second fixed contact; a catch mounted on said alli member and adapted to en age with contact when the latter is in circuitclosed position to hold the movable contact means against the fixed contact means to relea c said arm en t. 1 bimetallic member is sorted by generated by excessive electric current, the current path being provided through said bimetallic member and said contacts; resilient means tending to move said contact arm and movable contact mean carried thereby away from the fixed contact means when the contact arm is released by the catch on said bimetallic ine liber to break the current path; and manually operable double-acting means effective when moved in one di ection to release said contact arm from catch and when moved in the opposite direction to engage said contact arm with said catch A circuit breaker as forth in claim 2 which also includes a pair of resilient arms connected to the movable contact arm at one end and each supporting a movable contact at its other end, thereby assuring accurate engagement of the movable contacts with the fixed contacts.

i. A circuit breaker including: a case in which the circuit breaker mechanism is enclosed; a r movable cover closing said case; a bimetallic member having a pair of arms connected together at one end; a first electrical lead member secured within the case and connected to the end one arm of the bimetallic m mber and extending through a wall of the case; a first contact secured within the case and connected to the other end of the other arm of the bimeta c member; second d contact se- .1 the case in spaced relation to the contact; a second electric lead inemc nnected to the second fined contact and ing through a wall of the case; a movable contact arm guided for movement in said case; movable creact means mounted on said movable contact arm; a catch mounted on said bi metallic member and adapted to engage with said contact arm when the latter is in circuit-closed position to hold the movable contact means against the fixed contact means and to release sairf "an when the bimetallic member is distorted -eat generated by an electric current exceednrovidcd through said bimetallic member and contact resilient m ans tending to snap said contact arm and movable contact means carried thereby away from the fixed contact means when ing a predetermined value, the cur ent path being the circuit breaker mechanism is enclosed; a removabl cover adapted to close said case; a bimetallic member having a pair of ar he, eleca first al lead member connected to one arm of the bimetallic member and extending through a wall of the case; a first fixed contact connected to the other arm of the bimetallic member; a second fixed contact in spaced relation to the first fixed contact; a second electric lead member connected to said second fixed contact and exterding through a wall of the case; a movable contact arm guided for movement in said case; inovable contact means mounted on movable cont ct arm; catch means mounted on said bilic member and adapted to engage with said contact when the latter is in circuit-closed position hold the movable contact means nst the fixed contact means and release said arm when the bimetallic member is distorted by generated by an electric current exceeda predetermined value, the current path g provided through said bimetallic member id contacts; resilient means tending to said contact arm and movable contact Led thereby away from the fixed conn the contact arn. is released by means no br ak the current path; an 3' member extending through, and in a excluding relation with an opening in a wall 1e case; means effective, when actuated by cent of the operatin member in one direcc re ase said contact arm, and when moved site direction to engage said contact said catch means when the bimetallic member is in undistorted condition; and adjusting means for said bimetallic member extending into opening in the wall of said case, whereby fasting means may be operated from the r of said case to adjust the operation of bimetallic member.

6. A circuit breaker as set forth in claim 5, n which the bimetallic member is provided tovard its fixed end with a re-entrant portion affording an angular knee, and the adjusting means comprise a wedge of insulating material supported for sliding engagement with sai knee and a threaded rod engaging in a threaded hole in said wedge; a collar on said rod engaging against the adjacent wall of the case; and an end of rod projecting into a hole said Wall and formed for engagement w h a tool whereby the threaded rod may be turned to vary the position of the wedge.

7. A combined thermally-operated circuit breaker and switch including: a case; a plate secured to close the latter and provide a dustproof enclosure for the parts of the circuit breaker; a bimetallic member and fixed contact means mounted within the case, having electrical leads connected to said bimetallic member and fixed contact means, said leads projecting through a wall or" said case; a contact arm movably mounted within said enclosure; movable contact means mounted on said contact arm; catch means mounted on said bimetallic member and adapted to retain the contact arm in a position with the movable contact means engaged against the fixed contact means of the circuit breaker in the circuit-closed position of the parts; a manually operable member extending through the plate and engaging against the contact arm and bimetallic strip, whereby the contact arm may be operated to reset the breaker and when desired, to release the contact arm from the bimetallic member to manually break the circuit; and resilient means positioned within the case and urging the contact arm away from the fixed contacts so that when the contact arm is released by the bimetallic member due to distortion of the later from normal position caused by a current overload, the movable contacts are snapped away from the fixed contact means.

8. A combined thermally-operated circuit breaker and switch as set forth in claim 7 in which said contact arm comprises: a movable contact support pivoted to the contact arm, the movable contact means being mounted on said support at a point spaced from the pivotal axis thereof; an arm projecting from said support and positioned to engage and rest upon the bimetallic member when in position to engage the contact arm, said arm acting to rock the movable support about its axis to bring the movable contact means against the fiXed contact means; and a resilient means connected between the contact arm and movable contact support and stressed by said rocking movement of the support so that when the contact arm is released from the bimetallic member, the movable contact means are snapped out of engagement with the fixed contact means to break the circuit and cannot again be brought into engagement with the fixed contact means until the bimetallic member returns into position to engage the contact arm.

9, A combined thermally-operated circuit breaker and switch including: a case open on one side; a plate secured on said case over the open side and providing a dust-proof enclosure for the parts of the circuit breaker; a bimetallic member and fixed contact means mounted within the case having electrical leads connected to said bimetallic member and fixed contact means and projecting through a wall of the case; a contact arm movably mounted in said case; movable contact means mounted on said contact arm; catch means mounted on said bimetallic member and adaptedto maintain the contact arm with the movable contact means in engagement with the fixed contact means; a manually operable member extending through a wall of the case and engaging against the contact arm and the bimetallic strip whereby the contact arm may be operated to reset the breaker and when desired, to release the contact arm from the bimetallic member to manually break the circuit; and resilient means positioned within the case and urging the contact arm away from the fixed contacts so that when the contact arm is released by the bimetallic member due to distortion of the latter from normal position caused by a current overload, the movable contacts are snapped away from the fixed contact means.

10. A circuit breaker including: a mounting member supporting the circuit breaker parts a bimetallic member having a pair of arms connected together at one end, and secured at their other ends to the mounting member in series in an electric circuit; fixed contact means secured to said mounting member; a contact arm pivotally secured at one end to said mounting member; resilient means secured to said contact arm; movable contact means mounted on said resilient means and positioned so as to be brought into wiping engagement with said fixed contacts when the contact arm is rocked upon its pivotal axis to bring the movable contact means against the fixed contact means; a catch mounted on said bimetallic member and adapted to engage with said contact arm when the latter is in circuit closed position to hold the movable contact means against the fixed contact means and to release said arm when the bimetallic member is distorted by heat generated by an electric current greater than that which the bimetallic member is designed to carry without tripping, the current path being provided through said bimetallic member and said contacts; resilient means tending to snap said contact arm and movable contact means carried thereby away from the fixed contact means when the contact arm is released by the catch on said bimetallic member to break the current path; and manually operable double acting means effective when moved in one direction to release said contact arm from said catch and when moved in the opposite direction to engage said contact arm with said catch.

11. A circuit breaker which includes: a movable arm; a movable electrical contact mounted on said arm for movement therewith; a fixed electrical contact adjacent said arm and positioned to be engaged by said movable contact when said arm is in a first position, and separated from said movable contact when said arm is in a second position; resilient means urging said arm toward said second position; latch. means positioned to engage said arm and retain it in said first position, said latch means including an element responsive to the flow of current therethrough and acting to move said latch means to release said arm upon the passage of current exceeding a predetermined value; a manually operable means selectively movable in either of two directions, and having a portion adapted to bear against said movable arm and a cam surface adapted to bear against at least a portion of said latch means, movement of said manually operable means in one direction causing said portion to bear against said movable arm and urge it toward said first position where it is engaged by said latch, and movement of said means in the opposite direction causes said cam surface to bear against said portion of said latch means and urge the same to a position releasing movaole arm; and means connecting said currentresponsive element, said movable contact, and said fixed contact in series.

References Gited in the file of this patent UNITED STATES PATENTS Zeller July 19, 1949 

